August 2010

Estufas Patsari

31 August 2010 - 2:33pm

Berrueta

Victor Berrueta, GIRA, August 2010

Web site de la Proyecto PATSARI : http://www.patsari.org/

Mexico

Estufa patsari

A CONTINUOUS-FLOW RICE HUSK GASIFIER FOR THERMAL APPLICATIONS

24 August 2010 - 4:07pm

Belonio

Alexis T. Belonio, Daniel A. H. Belonio, and Lucio Larano, August 2010

This paper (see attached) describes a continuous-flow rice husk gasifier (CFRHG) designed and developed for various thermal applications such as cooking, drying, kiln firing, baking, and others. The technology follows the principle of a moving-bed, down-draft reactor converting raw rice husks into combustible gases that is rich in carbon monoxide (CO) and hydrogen (H2).

Different sizes were built and tested in collaboration with the private sector both in the Philippines and in abroad. The gasifier units which were built, tested and evaluated have varying reactor diameter, ranging from 0.40 to 1.20 m with a corresponding power output of 35.7 to 321.2 kWt. The rice husk consumption rate for the different reactor diameters tested ranges from 19 to 169 kg per hour. The specific gasification rate of the gasifiers was found to operate well at 150 kg/hr-m2. The temperature of the gas leaving the reactor varies from 150° to 270°C for all the units tested. The flame temperature reaches as high as 400° to 800°C, depending on the size of the reactor. The bigger the size of the reactor diameter, the higher is the flame temperature. The parasite load varies from 4.2% for the smaller diameter reactor to 1.5% for the bigger model. Combustible gases are generated within 5 to 30 minutes for the different sizes tested. The heating value of the gas ranges from 1200 to 1400 kcal/m3. And, only one person is needed to operate the small gasifier and two persons are needed for the big gasifier model.

Results of the tests showed that the CFRHG is convenient to use and its operation is easily controlled with the use of gas valves. There is no smoke emitted during operation. Black carbon content and tar emissions were found to be very minimal. The char produced can be used for agricultural application and the ash produced can be used for the production of low-cost construction materials.

Philippines

Rice Husk Gasifier

Rice Husks

Observations: Design Principles for Charcoal Stoves

24 August 2010 - 2:59pm

Roth, Christa

Christa Roth and Christoph Messinger, August 2010

Existing Charcoal Stove

Improved Charcoal Stove

Improving the Charcoal Stove for Haiti, Stove Camp 2010 (see the Stove Camp Summary for challenge details)

Main points mentioned at the end of the Stove Camp Workshop

We need a high turn down ratio.
To bring water and foods fast to the boil, we need high power in the heat-up phase.
However, thereafter we commonly need low power for simmering. The stove
therefore needs to offer the opportunity to turn down the power output drastically.
Options:
1. Regulation of primary air supply (e.g. closing door)
2. The gap between pot and charcoal is increasing over cooking time (shape of char container provides more depth = increased gap to the char)
3. c) The amount of char available at the end of cooking is reducing (conical shape of char container = less char over time available)
We need to reduce heat losses to the bottom and to the side of the stove.
A char container radiates heat to all sides – not just to the pot. To reduce the amount
of char used, it is important to reduce the heat losses to the other directions.
Options:
1. Bottom of stove: rebounding plate (with holes) in between primary air supply
2. intake and charcoal container. Thus primary air is channeled through the
3. heated rebounding plate, taking some heat back into the char container.
4. Side of the stove: double wall with air in between for insulation.
We need to maximize heat harvest from a given amount of charcoal.
Charcoal burning is mainly influenced by the amount of air available in the char
container.
Options:
1. A vertical spacer in the center of the charcoal container (Lanny Henson’s pig tail”) seemed to increase the availability of air for charcoal combustion.
2. Additional draft (e.g. forced air) may increase heat generation per time unit. However, this may also increase CO emissions and reduce efficiency of char use.
3. Secondary air to burn off the CO in a gap between the charcoal and the pot may provide additional heat. However, for this to be beneficial it may not impact on the surface area available for direct radiation from the charcoal to the pot and should not cool down the air in the gap (well preheated secondary air).
We need to maximise heat transfer to the pot.
Generating as much heat as possible out of a given amount of charcoal is one step.
But another important step is to make sure that most of this heat actually is
transferred into the cooking pot.
Options:
1. “Sunken pot” concept seems to provide best results in terms of heat transfer (Henson stove). Unfortunately, in real life this might not be possible in many work environments.
2. Best heat transfer is NOT achieved if the pot rests on the char. Optimum is about 1inch away from the char, not closer than that. For Simmer, this could increase to 2-3 inches.
3. A skirt is highly important to shield the gap area between the pot and the char against the influence of wind. The gap between pot and skirt should bedetermined.

Christa’s Summary of the stove camp

Observation and necessary action	Derived Design Principles
Charcoal radiates heat to all sides: as much can radiate towards the bottom of the stoves as can radiate upwards towards the pot. Action: Avoid loss of radiating and conducting heat from charcoal that is not directed towards the pot.	Add space between the charcoal grate and other stove parts: Lift the charcoal grate slightly off the bottom of the stove and increase the space to the sides of the stove. Limit the places where the hot grate can conduct heat to other stove parts. Add a deflector plate between charcoal chamber and the stove bottom to radiate heat back upwards. Insulate the stove bottom to prevent heat loss through the bottom. Insulate sides of the stove. Regain heat through air circulation (air cooling of stove) by passing air through heated stove parts thus preheating air entering the combustion system. This can be by passing primary air through the deflector plate below the grate and/or secondary air through a gap between double side walls of the stove.
Charcoal combusts in function of the available oxygen. Thus heat generation is a function of air supply to the charcoal grate. Action: get the right amount of air to the charcoal grate. To little will choke the combustion, too much will cool the flue gases.	If power of the stove is too low, increase air supply by making more holes in the grate. adding a ‘Henson pig-tail’ vertical air-pass through the charcoal bed. Do not pile the charcoal up too high, as this will restrict air flow through the charcoal bed (this is influenced as well by the shape and particle size of the charcoal chunks).
The combustion of charcoal goes from oxidizing C to CO, then in a subsequent step from CO to CO2. CO is a toxic gas and has still considerable energy value. Ensuring a complete combustion will increase energy output and reduce toxic emissions. Action: avoid CO emissions.
Charcoal radiates heat but there is also considerable convection of hot flue gases. Action: Optimize transfer of created heat into the pot.	Avoid obstructions between the radiating charcoal bed and the bottom of the pot (increase the view factor of the charcoal seeing the pot).

Improved Stove

24 August 2010 - 2:54pm

Baseline Stove

24 August 2010 - 2:54pm

Bundled Corn Stalk Stoves for Malawi, Stoves Camp 2010

24 August 2010 - 2:36pm

Still

Anderson

Dean Still, August 2010

One fine rainy morning two fine fellows from StrawJet (http://www.strawjet.com) , an Oregon company that makes equipment to bundle agricultural waste in Malawi, wandered into the lab and asked if it’s
possible to make a stove that uses bundled corn stalks to cook food. I said that I thought it was possible and after some conversation and testing of prototypes StrawJet put up a $250 prize to encourage Stove Camp participants to make it so.

Burning corn stalks leaves quite a bit of ash that does not fall apart but keeps its shape.
For this reason stoves must be adapted to deal with a lot of solid ash. Two types of stoves
were tested: 1.) A Jon Anderson Rocket Stove with lots of draft and a grate and 2.) Two
large TLUDs built by Paul Anderson and Art Donnelley that were vertically loaded.

Participants voted for the best stove that, in their opinion, was most effective. Jon
Anderson won the 2010 Cat Piss Award for a tall Rocket stove made entirely from found
materials that successfully burned the bundled corn stalks. The hope is that a pilot test
could be conducted in Malawi. If so, we’ll pass along the results.

Jon and his wife Flip have been in Haiti recently for three months helping folks to build
these kinds of Rocket stoves. They are beautiful, dedicated people, who like many folk at
Stove Camp, deserve real praise and adoration. I’m happy to send them some of both and
congratulations for making a wonderful stove!

Jon Anderson Corn Stalk Challenge Winner 2010 Stoves CAmp

24 August 2010 - 2:35pm

2010 Stoves Camp Corn Stalk Challenge

24 August 2010 - 2:34pm

Stoves Camp 2010 Charcoal Stoves for Haiti

24 August 2010 - 2:01pm

Stoves Camp 2010, Cottage Grove Oregon

Stoves Camp Participants

Fifty two high energy participants attended Stove Camp this year at Colgan’s Island, camping near the river, making and testing stoves, and listening to Fred’s Big Band harmonize so beautifully. Fred and his volunteers cooked breakfast every morning and dinners at nighttime parties on Rocket and TLUD institutional stoves.

Nick Salmons from International Lifeline Fund made a very successful Haitian charcoal stove that was voted “Best in Class” by his peers!

Stove Camp provides a venue for a gathered scientific community to advance knowledge of biomass cook stoves. Participants made new stoves and tested them daily for fuel use and emissions. Every morning the test data was shared and new stoves were constructed.

This year, a great deal of progress was made on charcoal stoves for Haiti. Camp participants, some of whom have worked in Haiti,designed a two-hour Water Boiling Test for Haiti, which uses a Haiti pot
and mimics a typical cooking task, cooking rice and beans. Charcoal stoves were constructed that used less fuel and produced less carbon monoxide compared to traditional Haitian stoves.

See the attached Stoves Camp Report for details of the tests, the interesting findings about the optimum charcoal to use for each stove, and pictures of the stoves tested.